This invention is related to a general service incandescent lighting unit, and more particularly, to a higher efficiency general service incandescent lighting unit having coaxial outer bulb and inner envelope with the inner envelope containing a halogen atmosphere along with a relatively high pressure fill-gas and a coaxially disposed low voltage filament therein.
The continuing pursuit of improving the efficiency of lamps is of increasing importance due to the increasing cost of energy. One of the family of lamps in which the efficiency is desired to be improved is the incandescent lamp. The incandescent lamps, although having efficiency ratings lower than those of fluorescent and high intensity discharge lamps, have many attractive features, such as, low cost, compact size, instant light, dimmability, convenience, pleasing spectral distribution, and millions of existing sockets in the homes of users who have become accustomed to the incandescent type lighting.
Incandescent lamps are of various types, the most well-known is the A-line which is typically termed a general service incandescent lamp having a wide range of wattage ratings. Still further, the general service incandescent lamp typically has a tungsten filament.
The tungsten filament is also commonly utilized in a relatively more expensive but more efficient special purpose halogen type lamps. In a typical operation over an extended period of time, some tungsten of the tungsten filament evaporates to the bulb wall, which, in turn, typically causes a darkening of the bulb wall, which, in turn, decreases the lumen output thereby decreasing the lumens per watt or efficacy of the lamp. It is known that the darkening of the bulb wall caused by the tungsten type filament may be substantially reduced by providing a halogen type gas atmosphere surrounding the tungsten type filament which provides a regenerative (transport) cycle that keeps the bulb wall clean resulting in improved efficacy or lumen output. The hereinbefore referenced U.S. patent application Ser. No. 519,165 describes means, such as, a halogen atmosphere employed within a general service incandescent lamp for improving its efficacy. It is still considered desirable that means for improving the efficacy, such as a halogen type atmosphere employed in a relatively expensive special purpose halogen type lamp be adapted to a general service incandescent lamp while maintaining the relatively inexpensive general purpose incandescent lamp.
Still further improvements are desired for relatively inexpensive incandescent type lamps. One such improvement is the use of an infrared reflecting film. The infrared type film operates so as to reflect the infrared type radiation back toward the filament while allowing the visible radiation to be emitted from the incandescent lamp. The infrared radiation is reflected back to the filament which recycles the energy that would be otherwise wasted, and, therefore, increases the efficacy of the general service incandescent type lamp. It is considered desirable to provide an incandescent lamp having an infrared type film.
Further still, with regard to an incandescent lamp having an infrared film to improve the operation of the filament, the desired operation of the infrared film must be taken into account with regard to the filament. For example, if the infrared film is comprised of an oxide, such as zinc oxide, in order to preserve the integrity the film it is desirable to locate and operate the film in an oxidizing atmosphere. Similarly, if the infrared film is comprised of a sulfide, such as zinc sulfide it is desirable to locate and operate the film in a nonoxidizing atmosphere. The desired operation of the infrared film may not be always achieved if the infrared film is subjected to a non-oxidizing atmosphere, typically provided by a fill-gas, such as xenon, krypton and argon, which are advantageous for the operation of the filament but not for an oxide infrared film. Accordingly, it is desired that the location of the infrared film of the general service incandescent lighting unit be provided with an atmosphere adapted to the desired operation of the particular infrared film.
Furthermore, with regard to the interrelationships between the infrared film, filament and the housing for the filament, the position of the filament relative to infrared radiation reflected by the infrared film must be considered. For example, it is desired that the filament be centrally located relative to the reflected infrared radiation so that the rays of infrared radiation emitted by the filament may be reflected by the infrared film in such a manner so as to impinge or strike the filament. Accordingly, it is desired that the filament along with its housing be centrally located relative to the infrared radiation reflected by the infrared film. This is accomplished by having the inner and outer envelopes and the filament coaxially disposed.
Further still, with regard to the positioning interrelationships between the infrared film and filament, the structural stability of the filament must be considered. For example, if a filament is initially advantageously centered with regard to the infrared reflected radiation, and then due to its operation experiences a distortion or sagging, the desired centering is degraded. Accordingly, it is desired that the filament be mechanically sturdy with a stable configuration type such as described in detail in the aforementioned U.S. Application Ser. No. 519,165.
The hereinbefore referred to U.S. patent application Ser. No. 519,165 describes a filament operated at a low voltage while maintaining the wattage and even increasing the efficacy of the general service incandescent lamp. It is still considered desirable to provide a filament that provides extended life and maintains the wattage of the lamp and even increases the efficacy of the incandescent lamp while operated at a low voltage.
Still further, it is considered desirable that the means for reducing the operating voltage be internally located within the housing of a general service incandesent lighting unit so as to form an integral device.
The operation of a tungsten filament may be further improved relative to the efficacy of the incandescent lighting unit by housing the filament in a suitable efficient fill-gas, such as xenon, krypton or argon, raised to a relatively high pressure. The high pressure fill-gas improves the operation of the filament by reducing the evaporation of the tungsten material from the filament and by allowing the filament operating temperature to be higher for equal lamp life, thus contributing to improving the efficacy of the lamp. The arc-out resistance of the filament, that is, the resistance of the filament to being burned out by an arc condition, may be improved by the addition of nitrogen gas. In a manner as previously described for the halogen atmosphere, the related U.S. patent application Ser. No. 519,165 describes means, such as, a high pressure fill gas of xenon, krypton or argon preferably having nitrogen gas employed within a general service incandescent lamp for improving its efficacy. It is still considered desirable to provide a general service incandescent lighting unit utilizing the efficacy gain realized by the high pressure fill gas of the xenon, krypton or argon, and to improve the arc-out resistance of the filament by the addition of the nitrogen gas.
Still further, it is considered desirable to provide an adaptive housing containing the high pressure fill-gases having the nitrogen additive along with the halogen gas and a tungsten filament. The housing being adapted for easy insertion onto and removal from the general service incandescent lighting unit.
Further still, it is considered desirable to provide an infrared type film for a general service incandescent lighting unit in such a manner so as to be easily attached to or detached from a general service incandescent lighting unit under initial fabrication and replacement conditions respectively.
Accordingly, objects of the present invention are to provide a relatively inexpensive general service incandescent lighting unit having, (1) an infrared reflecting film that reflects infrared radiation concentrically to the lamp filament and transmits visible radiation, (2) an infrared reflecting film that is located at a position sufficiently remote from the filament of the general service incandescent lighting unit and in an advantageous atmosphere to avoid film degradation, (3) a filament along with its housing that is centrally located relative to the infrared radiation reflected by the infrared reflecting film, (4) a mechanically sturdy filament which maintains its central position relative to the reflected infrared radiation during the operation of the filament, (5) a low voltage filament operated at a reduced applied voltage while still maintaining its wattage and even improving lamp efficacy, (6) means internally located in the general service incandescent lighting unit for reducing the voltage that is applied to the low voltage filament, (7) a low voltage filament housed within an atmosphere comprised of a halogen and a relatively high pressure fill-gas such as xenon, krypton or argon, and nitrogen gas, ( 8) a light-transmissive infrared reflective film provided on a housing which is easily attachable to and detachable from the remainder of the general service incandescent lighting unit under initial fabrication and replacement conditions respectively, and (9) comprising a combination of the contributions from the infrared reflecting film, the advantageous location of the infrared film, the centrally located filament, the sturdy low voltage filament, the means for reducing the applied voltage, the housing of the filament having an atmosphere comprised of a halogen, a high pressure fill-gas such as xenon, krypton or argon and the nitrogen additive, and the infrared film on a housing having means so as to be easily attachable and detachable from the general service incandescent lighting unit, in such a manner that the overall effect of the combination is greater than expected gains anticipated from the individually contributing features.
These and other objects of the present invention will become apparent upon consideration of the following description of our invention.